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Avalanche Forecast

Archived

Jan 14th, 2023–Jan 15th, 2023

Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches possible, human triggered probable.
Below Treeline
Natural avalanches unlikely, human triggered possible.
Alpine
Natural avalanches unlikely, human triggered possible.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely.
Alpine
Natural avalanches unlikely, human triggered possible.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely.

Regions

South Coast Inland, Birkenhead, Duffey, South Chilcotin, Stein, Taseko.

Avalanche hazard is improving but be mindful that deep instabilities are still present. Uncertainty is best managed through conservative terrain choices.

Confidence

Moderate

Avalanche Summary

On Friday, snowcats remotely triggered numerous size 2.5 persistent slab avalanches on surprisingly low angel terrain from up to 150 m away. Avalanches occurred on a crust covered by surface hoar found up to 1900 on north and easterly aspects. See MIN for good photos and more details.

Several skier-triggered storm slab avalanches were reported up to size 1.5 throughout the region.

On Thursday, several natural loose wet avalanches, to size 1, were observed below treeline. Several explosive-triggered, size 1.5 storm slab avalanches were reported.

Thanks for the observations and please continue to post your reports and photos to the Mountain Information Network. It is really helpful for forecasters!

Snowpack Summary

20-30 cm of new snow and southerly winds have built storm slabs in lees at higher elevations. Below 1900 m storm brought a mix of rain and snow which will likely harden into a crust as freezing levels drop.

50 to 70 cm down is a crust formed in late December. Between 1900 and 1700 m surface hoar can be found above this crust which was reactive with the new snow load on Friday. This crust varies in thickness throughout the terrain and elevation. Uncertainty remains about the robustness of this crust above 2100 m.

There is a widespread weak layer of facets and depth hoar at the bottom of the snowpack. Snowpack depths around treeline are about 150-180 cm deep. The snowpack below treeline is very shallow and faceted.

Weather Summary

Saturday Night

Clear with cloudy periods. Southeast winds of 20 km/h. Ridgetop low-temperature -4C. Freezing levels fall to 500 m.

Sunday

Mainly cloudy isolated flurries, trace accumulation. Light variable winds gusting 20 km/h. Ridgetop high-temperature -2C. Freezing levels 1200 m.

Monday

Mainly cloudy with scattered flurries tapering off in the afternoon, 2-5 mm. Light variable winds gusting 20 km/h. Ridgetop high-temperature -3C. Freezing levels 1000 m.

Tuesday

Mainly cloudy with isolated flurries, 2-5 mm. Southwesterly winds increase from moderate to strong through the day, gusting 50 km/h. Ridgetop high-temperature -5C. Freezing levels valley bottom.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

  • Surface hoar distribution is highly variable. Avoid generalizing your observations.
  • Caution around convexities or sharp changes in terrain.
  • Storm slabs in motion may step down to deeper layers resulting in large avalanches.

Problems

Storm Slabs

Storm Slab avalanches are the release of a cohesive layer (a slab) of new snow that breaks within new snow or on the old snow surface. Storm-slabs typically last between a few hours and few days (following snowfall). Storm-slabs that form over a persistent weak layer (surface hoar, depth hoar, or near-surface facets) may be termed Persistent Slabs or may develop into Persistent Slabs.

Persistent Slabs

Persistent Slab avalanches are the release of a cohesive layer of snow (a slab) in the middle to upper snowpack, when the bond to an underlying persistent weak layer breaks. Persistent layers include: surface hoar, depth hoar, near-surface facets, or faceted snow. Persistent weak layers can continue to produce avalanches for days, weeks or even months, making them especially dangerous and tricky. As additional snow and wind events build a thicker slab on top of the persistent weak layer, this avalanche problem may develop into a Deep Persistent Slab.